Refridgerating device with a temperature sensor

ABSTRACT

A refrigerating device is equipped with a temperature sensor in the form of an infrared sensor ( 7 ), for detecting an operating temperature of the device. Said infrared sensor ( 7 ) is located on a board ( 5 ) in a non-refrigerated are of the refrigerating device, together with a control circuit.

[0001] The invention relates to a refrigerating device with atemperature sensor for detecting an operating temperature of therefrigerating device.

[0002] In refrigerating devices such as refrigerators, freezers orcombination appliances an operating temperature such as an interiortemperature or the temperature of an evaporator are conventionallydetected using temperature-dependent resistances which are connected viaa cable harness to a control circuit to regulate the refrigeration.

[0003] This technology which has been in normal use for a long time hasvarious disadvantages. Firstly, it is necessary to attach thetemperature-sensitive resistance directly at the location whosetemperature is to be detected. However, the control circuit whichregulates the operation of a refrigerating machine using the temperaturedetected by the temperature sensor is usually located in a nonrefrigerated outer area of the refrigerating device in order to avoidmalfunctions caused by condensate formation on the control circuit. Thespatial separation of the control circuit and the temperature sensorforced thereby makes these complicated and therefore expensive toattach.

[0004] Wiring is required to feed the measurement signal of thetemperature-sensitive resistance to the control circuit. This wiring issensitive to disturbances caused by electromagnetic stray effects. Inaddition, the detected temperature is not necessarily the temperature ofthe location to be monitored but the temperature established in thetemperature-sensitive resistance. In order to avoid falsifications ofthe temperature measurement, it is thus necessary to insulate thisefficiently from the non-refrigerated outer area.

[0005] Especially when such a conventional temperature sensor is used tomonitor the temperature of an evaporator, the strong temperaturefluctuations to which such a sensor is exposed and which can extend from−40° C. under normal refrigeration as far as +8° C. during defrosting,lead to considerable mechanical stresses on the insulation of thetemperature sensitive resistance which can result in failures.

[0006] The object of the present invention is to provide a refrigeratingdevice with a temperature sensor wherein the installation of thetemperature sensor is simplified, wherein the sensitivity of themeasurement signal of the temperature sensor to electromagnetic strayeffects is reduced and wherein any failure as a result of thermalstresses is eliminated.

[0007] This object is achieved by a refrigerating device according toclaim 1.

[0008] The operating temperature to be detected by the infrared sensorof this refrigerating device can be an interior temperature of therefrigerating device. In this case, a black body with which the infraredsensor is in visual contact can be provided in the interior of therefrigerating device.

[0009] The temperature of an evaporator of the refrigerating device canalso be considered as the operating temperature to be measured. In thiscase, the infrared sensor is advantageously in visual contact with asurface of the evaporator facing the interior of the refrigeratingdevice. This allows the temperature of this surface of the evaporatorrelevant for the cooling of the interior to be measured directly insteadof the temperature of the back side which is easier to achieve inmeasurements using a temperature-sensitive resistance but may befalsified by a heat inflow from outside. Since the infrared sensor neednot be located in direct contact with the object whose temperature it isto measure, it is possible to locate said sensor in the immediateneighbourhood of the control circuit, especially on a common board withthe control circuit; thus the control circuit and the temperature sensorcan be prefabricated as a structural unit and built into therefrigerating device according to the invention jointly duringinstallation.

[0010] Since the temperature of the infrared sensor is not decisive forthe measurement result, said sensor can be attached in anon-refrigerated outer area of the refrigerating device. In such a caseit is desirable that it is separated from the measurement surface to bemonitored by an infrared-transparent window which blocks an unhinderedinflow of heat into the interior of the refrigerating device.

[0011] If the distance between the infrared sensor and the measurementsurface to be monitored by it is large, it is desirable to provide alens between the two to image the measurement surface on aradiation-sensitive surface of the sensor. This lens can especially formthe afore-mentioned window at the same time.

[0012] Further features and advantages of the invention are deduced fromthe following description of embodiments with reference to the appendeddrawings wherein:

[0013]FIG. 1 is a schematic section through a part of the housing of arefrigerating device according to the invention according to a firstembodiment of the invention; and

[0014]FIG. 2 is a similar section according to a second embodiment ofthe invention.

[0015]FIG. 1 shows a highly schematic section through the upper frontcorner of the housing of a refrigerating device according to theinvention. The refrigerating device comprises a thermally insulatinghousing of which a part of an upper side 1 and a front side 2 with adoor 3 mounted thereon can be seen in FIG. 1.

[0016] Mounted above the door 3 on the front side 2 is a screen 4 whichcan be a simple plastic moulding without any substantial thermalinsulation effect of its own.

[0017] In the space enclosed by the screen 4 and the front side 2 thereis a control circuit on a board 5 and an infrared sensor 7 mounted onits surface facing the interior 6 of the refrigerating device. Such aninfrared sensor can detect the intensity of infrared radiation invarious spectral ranges and allows the temperature of the radiationsource to be inferred from the intensity distribution. This infraredsensor can, for example, be of a similar type to those used in so-called“ear thermometers” for measuring body temperature. The infraredradiation from the interior of a refrigerating device is certainlysignificantly weaker and on average of longer wavelength than that ofthe human body but the requirements on the measurement accuracy forregulating a refrigerating device are significantly lower than those forbody temperature measurements so that such an infrared sensor isconsidered suitable for regulating a refrigerating device.

[0018] The attachment of the board 5 with the control circuit in thefront area of the refrigerating device has the advantage that it ispossible to mount display elements such as a light-emitting diode 8 onthe board 5, said display elements being visible for a user through awindow 9 of the screen 4 so that the user can easily confirm that therefrigerating device is operating correctly at any time. Regulators, forexample, for setting a desired temperature of the interior, can also bemounted directly on the board 5 and are nevertheless easily accessiblefor a user.

[0019] The infrared sensor 7 is located opposite a window 10 let intothe front side 2 and made of an infrared-transparent material, throughwhich the characteristic thermal radiation of a black body 11 mounted inthe interior 6 can pass substantially unhindered onto theradiation-sensitive surface of the infrared sensor 7.

[0020] With the aid of the black body 11 it is possible to specificallymeasure the temperature in a critical area of the interior 6. Such anarea is precisely the front upper area of the interior 6, where theblack body 11 is shown in the figure because the highest temperatures ofthe interior are generally established here as a result of the heatinflow into the interior 6 which is strongest along the edges of thedoor 3.

[0021] However, it is also possible to omit the black body 11 so thatthe infrared sensor 7 to a certain extent has a “free view” into theinterior 6 through the window 10. In thermal equilibrium this interior 6also has the radiation characteristic of a black body; so that byomitting the black body 11, a temperature averaged over the entire fieldof view of the infrared sensor 7 can be measured using the infraredsensor 7. Such an arrangement has the peculiarity that the measurementvalues detected by the infrared sensor 7 can be “falsified” if chilledgoods which have only just been loaded into the refrigerating device andhave not yet acquired its inner temperature, are located in its field ofview. The infrared radiation power of a body increases substantiallymore strongly than linearly with its temperature. Such “warm” chilledgoods can thus to a certain extent “swamp” their cold environment. Insuch a case, the temperature detected by the infrared sensor is higherthan the arithmetic mean of the temperature formed taking into accountthe “warm” chilled goods. However, such a falsification can beabsolutely desirable because it allows the refrigeration capacity of therefrigerating device to be set high before the heat brought in with thenew chilled goods has spread in the interior. In this way, heating ofthe interior by newly brought-in relatively warm chilled goods isreliably prevented without any expensive circuitry measures beingrequired for this.

[0022]FIG. 2 shows a section similar to that in FIG. 1 through a furtherdeveloped variant of a refrigerating device according to the invention.In addition to the elements already shown in FIG. 1 and described above,FIG. 2 also shows part of the back wall 13 of its housing and anevaporator plate 14 arranged thereon. In this variant the window 10 isreplaced by a lens 15 which is made of the same material as the window10 and can be let into the front side 2 of the housing in acorresponding fashion.

[0023] The lens 15 has the effect that the field of view 16 of the lensdelimited by the dashed lines in FIG. 2 is limited compared with theembodiment in FIG. 1 and merely covers a limited area 17 of theevaporator plate 14. With this arrangement the temperature of theevaporator plate 14 can be precisely monitored transversely through theinterior 6.

[0024] Since the infrared sensor 7 is not itself exposed to thetemperature fluctuations in the evaporator plate, its lifetime is notadversely influenced hereby and disturbances in the operation of therefrigerating device are avoided.

[0025] Various further developments of the embodiments described aboveare possible within the framework of the present invention. For example,it is feasible to mount a plurality of infrared sensors on the board 5,each monitoring a field of view in the interior 6 of the refrigeratingdevice via their own window. Such differentiated temperature monitoringmakes it possible for the control circuit to differentiate, for example,between newly inserted chilled goods, which merely lead to locallyincreased measured temperature values, and a general functional disorderwhen the temperature of the entire interior 6 rises as a result offailure of the cooling.

1. A refrigerating device with a temperature sensor for detecting anoperating temperature of the device, characterised in that thetemperature sensor is an infrared sensor (7).
 2. The refrigeratingdevice according to claim 1, characterised in that the operatingtemperature is the temperature of an interior (6) of the refrigeratingdevice.
 3. The refrigerating device according to claim 2, characterisedin that the infrared sensor (7) is in visual contact with a black body(11) located in the interior (6).
 4. The refrigerating device accordingto claim 1, characterised in that the operating temperature is thetemperature of an evaporator (14) of the refrigerating device.
 5. Therefrigerating device according to claim 4, characterized in ithat theinfrared sensor (7) is in visual contact with a surface of theevaporator (14) facing the interior (6) of the refrigerating device. 6.The refrigerating device according to one of the preceding claims,characterised in that the infrared sensor (7) is connected to a controlcircuit for the operating temperature and is located in the immediateneighhourhood thereof.
 7. The refrigerating device according to claim 6,characterised in that the infrared sensor (7) is located on a commonboard (5) with the control circuit.
 8. The refrigerating deviceaccording to one of the preceding claims, characterised in that thetemperature sensor is attached in a non-refrigerated outer area of therefrigerating device and is separated from a measuring surface to bemonitored by means of an infrared-transparent window (10, 15).
 9. Therefrigerating device according to claim 8, characterised in that thetemperature sensor is accommodated below a front screen (4) of therefrigerating device.
 10. The refrigerating device according to one ofthe preceding claims, characterised by a lens (15) for imaging ameasuring surface (17) on a radiation-sensitive surface of thetemperature sensor.